Putting DNxHD Through Its Post Paces

Working in conjunction with Avid, PostWorks, New York, the downtown-Manhattan Nirvana for indie-film DIs and other demanding post projects, last month hosted a split-screen demonstration of imaging technology that it says is starting to change the way filmmakers think about post in general – and DIs in particular.

Using footage from Padre Nuestro, an indie feature currently in post that's racing a deadline for its Sundance Film Festival debut in January, the PostWorks tech team built a strong case for the 4:4:4 DI, executed using the HDCAM SR tape format and leveraging DNxHD technology in the post pipeline.

First, using a 2K digital cinema projector in the PostWorks DI screening room, they showed a split-screen comparison of the original 2K film scan and the 4:4:4 HD version of the same footage. It's fair to say that under those screening conditions, the two sides of the frame were basically indistinguishable. Next, they argued for the advantages of Avid's DNxHD codec in the DI process by comparing a 4:2:2 HD conversion to mastering-quality Avid DNxHD running at 175 Mbps. The difference was perhaps vaguely detectable in the film's grain structure – but a casual viewer would detect no image degradation at all. Finally, the team compared Avid DNxHD running at a much more manageable 36 Mbps to the traditional 14:1 compression of the editorial workflow. Here, there was almost no comparison – DNxHD was the better choice by a country mile.

The implications of that last taste test are remarkable, the PostWorks team said, because they suggest that editors are finally in a position to jettison the idea that an offline edit must be done using coarse standard-definition images. The storage and bandwidth demands required to work at 36 Mbps aren't trivial – but it will get editors that much closer to the original image. PostWorks Senior Technical Adviser Joe Beirne compared it to the old days of film cutting, when images were very small but were still seen on film, through ground glass, where critical viewing could take place. "In many respects," said PostWorks Director of Technology Matt Schneider, "it sort of makes the offline process go away."

 

Cinematographer Igor Martinovic told Film & Video after the screening that Padre Nuestro is only one of two films that he will have at Sundance next month. The other is the feature Das Fräulein, from Swiss director Andrea Staka, which won the top prize at the Locarno International Film Festival earlier this year. Padre Nuestro was shot in Super 35 and scanned at 2K for a 4:4:4 DI using HDCAM SR. By contrast, Das Fräulein was shot in Super 16 and then blown up, optically, to 35mm. "I'm very glad we did it that way," he says, "and I'm glad we did Padre Nuestro as a DI."

The difference comes down to his particular visual ambitions for the newer film, which features a lot of dark, moody cinematography where the ability to see details in deep shadows is important. You could achieve a similar goal photochemically, using a bleach-bypass process to retain some of the detail – "but you see that look so often these days, in commercials especially," says Martinovic. Instead, Martinovic made a deliberate decision to go gritty, choosing an older, high-contrast Kodak stock dating back to the early 1980s – before the Vision2 line-up was engineered to reduce grain to a minimum.

Because he knew from the start of photography that Padre would receive a DI, Martinovic was able to move more quickly on set. "It makes a difference in gripping," he notes. "You may be putting up flags, and you'll decide while you're setting up that you don't really need to put those two last flags up in a certain place, because in the DI you can use power windows to bring up that part of the image."

Gaining all that control still demands some compromise, and Martinovic agrees that, no matter how good they look, prints still have a certain quality that reveals, to the trained eye, that the source material went through a DI process. But he's already looking to the next generation of technology to help smooth that out. "With 4K," Martinovic says, "I think that will go away."

Is Padre Nuestro going to be screened from film or HDCAM at Sundance? Martinovic says that's still up in the air, depending on whether a film-out of the finished project can be made in time for the deadline. But he expects PostWorks' Beirne will be on hand in Park City and doing his level best to make every screening, film or digital, look the best it possibly can.